1. Field of the Invention
The invention relates to a diazotization process for amines. More particularly, the invention relates to a diazotization process for producing azo dye compounds.
2. Description of Related Art
Numerous diazotization processes for primary aromatic amines are known. Many of these processes are commercially important because of their use in the production of dyestuffs. The most commercially significant diazotization processes are batch processes carried out at temperatures from -5.degree. to +5.degree. C. and use nitrous acid (HONO) as the diazotizing agent. It is formed in situ from NaNO.sub.2 and HCl producing significant amounts of salt that must be separated from the dye and discarded as hazardous waste. In most processes, a large excess of HCl is used. This is neutralized during the ensuing coupling reaction producing more salt that also must be removed and discarded. Both the separation and disposal of the salt are costly procedures. To form an azo dye, the aromatic diazonium ion is coupled with a second electron rich molecule (i.e. coupler) or coupling agent to form the dye.
Some unreactive or insoluble amines cannot be diazotized in aqueous solution. Many of these are diazotized using nitrosylsulfuric acid prepared by dissolving sodium nitrite in 90 to 96 percent sulfuric acid at 0.degree. C. to 10.degree. C. The nitrosylsulfuric acid is added to a solution of the arylamine in 96 percent sulfuric acid at 0.degree. C. to 10.degree. C. The diazonium compound is then coupled with an amine, a phenol, or any molecule which offers electron pair availability to form an azo linkage.
A process for producing diazonium ions without by-product salt would offer advantages and be environmentally desirable. No such commercial process is known to be in operation.